Common carotid artery flow velocity measurements in the newborn period with pulsed Doppler technique.

Using a commercial pulsed Doppler (PD) system we measured common carotid artery (CCA) flow velocities in 19 healthy and 6 stable preterm infants and computed volume flow rates based on the time-averaged flow velocities and vessel diameter. The mean (+/- SEM) time-averaged CCA velocities in the term and preterm infants were 33.04 +/- 3.0 and 23.3 +/- 1.3 cm.s-1, respectively. The total flow volume was significantly higher in the term as opposed to preterm infants: 126 +/- 11.2 vs. 55.6 +/- 7.7 ml/min (p less than 0.01). The body-weight-normalized flow volume, however, was not statistically significantly different between the two groups of infants. Several technical and practical limitations still exist to compute cerebral blood flow (CBF) volume accurately. In a puppy model we measured the CCA flow volume by electromagnetic flowmeter technique, and the PD device simultaneously. The correlation coefficient between 32 pairs of measurements was 0.93 (p less than 0.005). We conclude that commercial PD devices provide accurate velocity data, and under experimental conditions, the computed volume flow rates are accurate. Although in clinical situations reasonably accurate CBF values can be estimated, refinements in technology are needed to adopt this method as a possible means of measuring CBF at the bedside.